Poly-L-Lactic Acid Fillers Improved Dermal Collagen Synthesis by Modulating M2 Macrophage Polarization in Aged Animal Skin

Preliminary Evaluation of Improvements in Melasma and Photoaging With Laser-Driven Microjet Injection of Poly- d , l -Lactic Acid

BACKGROUND

Melasma, a common skin hyperpigmentation disorder, has traditionally been linked to hormonal changes in genetically predisposed individuals. Recent studies, however, highlight the role of photoageing, particularly from visible light exposure, as a significant contributing factor. Effective treatments for melasma and associated signs of photoageing remain a clinical challenge.

OBJECTIVE

This study aimed to evaluate the efficacy and safety of Poly-d,l-lactic acid (PDLLA) delivered via laser-induced microjet injectors in treating melasma and signs of photoageing.

PATIENTS AND METHODS

Eighteen Korean participants aged 42 to 74, with Fitzpatrick skin types III to IV, were enrolled. All participants exhibited melasma, signs of photoageing, or both. PDLLA was administered using the Mirajet device over 5 to 9 sessions. Clinical outcomes were assessed using the modified Melasma Area and Severity Index (MASI) and the Glogau Classification for photoageing. Adverse events were monitored throughout the study.

RESULTS

Significant improvements were observed in both melasma severity and signs of photoageing. The mean MASI score decreased from 22.72 to 7.31 ( p =.004). Photoageing severity, as assessed by the Glogau Classification, also improved notably. Minimal side effects were reported, primarily transient bleeding.

CONCLUSION

PDLLA administered via laser-induced microjet injectors appears to be a safe and effective treatment for melasma and photoageing, particularly in patients with more severe melasma. These findings suggest the potential for PDLLA in skin rejuvenation; however, further randomised controlled trials are warranted to confirm these results and optimise treatment protocols.

Sonographic Analysis of CureJet Injection Depth Consistency After Abdominal Stretch Mark Treatment Using Hyperdiluted Calcium Hydroxylapatite

Background

This study investigates the effectiveness and consistency of needle-free jet injectors in administering injections at uniform depths, particularly for the treatment of stretch marks. Ensuring consistent injection depth is crucial for achieving optimal therapeutic outcomes, especially when dealing with challenging skin conditions like stretch marks.

Methods

A retrospective study was conducted involving 25 patients treated for abdominal stretch marks using a needle-free injector (CureJet). For each patient, 10 injection sites were assessed via ultrasound, and the depth of the injections was measured. The mean injection depths and standard deviations were calculated for each patient to assess the consistency of injections. The injected substance was diluted calcium hydroxylapatite, a well-known biostimulatory agent used for skin rejuvenation. Injections were repeated over multiple sessions with consistent parameters to evaluate the reproducibility of the technique.

Results

The mean injection depth across patients was 0.5126 cm, with considerable variability observed between patients. The standard deviation ranged from 0.0326 to 0.2132 cm, indicating significant differences in the consistency of injection depths. The statistical analysis demonstrated that the needle-free injector achieved variable depths, with some injections penetrating deeper than intended, whereas others remained superficial.

Conclusions

While needle-free injectors like CureJet provide a promising alternative to conventional needles, achieving consistent injection depths remains a challenge. This study highlights the need for further refinement in injector technology and technique to improve uniformity in treatment depth, particularly for applications like scar treatment and stretch mark reduction. Enhancing precision in such devices could lead to better patient outcomes and increased safety in aesthetic treatments.

Increasing collagen synthesis in fibroblasts: The roles of PCL microspheres and the SAMD11-PLOD1 axis in skin rejuvenation

The degradation of extracellular matrix proteins such as collagen and elastin with aging leads to skin sagging. Polycaprolactone (PCL) microspheres are used as facial fillers because of their ability to provide volume, biodegradability, and collagen-stimulating properties. The direct biological effects of PCL microspheres on fibroblasts, particularly in stimulating sustained collagen production, require further investigation. We detected the safety and effect of PCL microspheres on human fibroblasts and investigated new collagen synthesis and the thickness of C57BL/6 mouse skin. Through an RNA-seq analysis of differentially expressed genes, we identified a key regulator of collagen production in PCL-stimulated fibroblasts. Our research revealed that PCL microspheres are safe for human fibroblasts, promoting their proliferation and increasing new collagen synthesis and skin thickness. We identified sterile alpha motif domain containing 11 (SAMD11) as a key regulator of collagen production in PCLstimulated fibroblasts through an RNA-seq analysis. By increasing SAMD11 expression, PCL microspheres increase collagen synthesis and rejuvenate skin through the upregulation of procollagen-lysine, 2-oxoglutarate 5-dioxygenase 1 (PLOD1). This study elucidates the mechanism by which SAMD11 regulates the effects of PCL microspheres as collagen stimulants for skin rejuvenation, providing a foundation for the future development and refinement of similar materials.

Development and Characterization of PEGylated Poly D,L-Lactic Acid Nanoparticles for Skin Rejuvenation

Recently, various biocompatible and biodegradable materials have garnered significant attention as cosmetic fillers for skin rejuvenation. Among these, poly ε-caprolactone (PCL), poly L-lactic acid (PLLA), poly D,L-lactic acid (PDLLA), and polydioxanone (PDO) microspheres have been developed and commercialized as a dermal filler. However, its irregularly hydrophobic microspheres pose hydration challenges, often causing syringe needle blockages and side effects such as delayed onset nodules and papules after the procedure. In this study, we synthesized a polyethylene glycol-poly D,L-lactic acid (mPEG-PDLLA) copolymer to address the limitations of conventional polymer fillers. Comprehensive characterization of the copolymer was performed using nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The mPEG-PDLLA copolymers demonstrated a unimodal size distribution of approximately 121 ± 20 nm in an aqueous solution. The in vitro cytotoxicity and collagen genesis of mPEG-PDLLA copolymers were evaluated using human dermal fibroblast cells. In this study, angiogenesis was observed over time in hairless mice injected with mPEG-PDLLA copolymers, confirming its potential role in enhancing collagen synthesis. To assess the inflammatory response, the expression levels of the genes MMP1 and IL-1β were analyzed. Additionally, gene expression levels such as transforming growth factor-β and collagen types I and III were compared with Rejuran® in animal studies. The newly developed collagen-stimulating PEGylated PDLLA may be a safe and effective option for skin rejuvenation.

Evaluating Poly-D,L-Lactic Acid for Lower Eyelid Rejuvenation: Efficacy and Safety

BACKGROUND

Injectable fillers like PDLLA offer a novel approach to addressing lower eyelid rejuvenation. Despite their growing popularity, comprehensive studies on newer products like PDLLA are limited.

AIMS

This study evaluates the efficacy and safety of PDLLA (Juvelook, VAIM Inc., Seoul, Korea) for treating tear trough deformities in Korean women, aiming to provide a long-term, minimally invasive solution for periorbital rejuvenation.

MATERIALS & METHODS

A selected group of Korean women exhibiting tear trough deformities underwent treatment with PDLLA. Patients were assessed pre-treatment and followed up at 1 week, 1 month, and 6 months post-treatment, with outcomes measured by independent clinicians using the Hirmand classification and patient satisfaction scores.

RESULTS

PDLLA demonstrated significant improvements in tear trough deformities with high patient satisfaction and minimal adverse effects. Follow-up results showed sustained improvements and no severe complications, indicating a safe profile for PDLLA.

DISCUSSION

The study highlights PDLLA's potential advantages over traditional fillers, including longer-lasting effects and enhanced collagen production, suggesting it as a superior option for those seeking durable aesthetic improvements.

CONCLUSION

PDLLA is an effective and safe treatment for periorbital rejuvenation in Korean women, providing lasting benefits and high patient satisfaction, warranting further comparative studies for broader applications.

The Efficacy of Thermal Mechanical Fractional Injury System for Facial Rejuvenation: Subjective, Objective and Image Analysis Study

BACKGROUND

Facial aging is the result of a number of factors, including the resorption of skeletal tissue, the atrophy of fat pads, and the laxity of connective tissue. These factors contribute to a reduction in facial volume and the development of skin changes. Thermal mechanical fractional injury (TMFI) represents a minimally invasive solution, stimulating collagen production and enhancing the delivery of topical formulations via epidermal microcraters.

AIM

This study seeks to evaluate the effects of TMFI on skin quality and introduce quantifiable methods to assess improvements.

PATIENTS AND METHODS

Adult patients seeking facial rejuvenation underwent three TMFI sessions, with a one-month interval between each session. The assessment of skin quality was conducted using the Scientific Assessment Scale of Skin Quality (SASSQ), which was completed by blinded experts. Patient satisfaction was evaluated using the FACEQ scale. Additionally, objective texture analysis was performed using the MAZDA program, which quantified surface irregularities.

RESULTS

The objective assessments demonstrated statistically significant improvements in the following parameters: roughness, wrinkles, pore size, elasticity, pigmentation, and erythema (p < 0.001). The FACE-Q results demonstrated high patient satisfaction, with a response rate of 68.4%. The MAZDA analysis confirmed significant texture improvements across most facial zones, with the exception of the medial forehead.

CONCLUSIONS

The findings of this study indicate that TMFI is an effective intervention for improving skin quality in a diverse range of patients. This study contributes to the existing literature on TMFI, which supports its use as a valuable tool in the field of skin rejuvenation.

Effects of Poly-L-Lactic Acid Fillers on Inflammatory Response and Collagen Synthesis in Different Animal Models

BACKGROUND

The responses to poly-L-lactic acid (PLLA) filler implantation exhibit variability across various animal models. This study aimed to investigate these differences in order to identify suitable animal models for diverse experimental applications.

METHODS

PLLA fillers were implanted into two distinct skin layers (periosteum and subcutaneous tissue), in rabbits, guinea pigs, rats, and mice. At 1, 2, 4, and 12 weeks postimplantation, biopsy samples were collected for hematoxylin and eosin staining, Masson's trichrome staining, and enzyme-linked immunosorbent assay (ELISA) to evaluate the differential responses among the animals.

RESULTS

All four animal models exhibited significant inflammatory responses and collagen regeneration following PLLA injection. However, the magnitude of these responses varied across species, with guinea pigs and rabbits displaying the most pronounced inflammatory responses, whereas mice exhibited the mildest. The degree of response also differed between tissue layers, with rats and mice showing stronger inflammatory responses in the periosteum compared to the subcutaneous tissue; a phenomenon not observed in rabbits and guinea pigs. ELISA analysis revealed upregulated TNF-α, IL-12, and TGF-β expression in rats and mice at 12 weeks.

CONCLUSIONS

Varying levels of tissue responses are observed following PLLA injections in different animals and within different tissue layers within a single animal. These findings suggest a careful selection of appropriate animal models is necessary for specific research objectives.

Synergetic role of TRPV4 inhibitor and mechanical loading on reducing inflammation

Resolution of inflammation is essential for normal tissue healing and regeneration, with macrophages playing a key role in regulating this process through phenotypic changes from a pro-inflammatory to an anti-inflammatory state. Pharmacological and mechanical (mechanotherapy) techniques can be employed to polarize macrophages toward an anti-inflammatory phenotype, thereby diminishing inflammation. One clinically relevant pharmacological approach is the inhibition of Transient Receptor Potential Vanilloid 4 (TRPV4). This study investigates the effects of various mechanical loading amplitudes (0%, 3%, and 6%) and TRPV4 inhibition (10 µM RN-1734) on the phenotypic commitments of pro-inflammatory (M1) macrophages within three-dimensional (3D) collagen matrices. M1 macrophages exposed to 3% mechanical strain exhibited upregulated pro-inflammatory responses, including increased pro-inflammatory gene expression and enhanced proteolytic activity within the extracellular matrix. TRPV4 inhibition partially mitigated this inflammation. Notably, 6% mechanical strain combined with TRPV4 inhibition suppressed Mitogen-Activated Protein Kinase (MAPK) expression, leading to reduced pro-inflammatory gene expression and increased anti-inflammatory markers such as CD206. Gene expression analysis further demonstrated significant reductions in pro-inflammatory gene expression and a synergistic promotion of anti-inflammatory phenotypes under TRPV4 inhibition at 6% mechanical strain. Surface protein analysis via immunohistochemistry confirmed these phenotypic shifts, highlighting changes in the expression of CD80 (pro-inflammatory) and CD206 (anti-inflammatory) markers, alongside F-actin and nuclear staining. This research suggests that TRPV4 inhibition, combined with specific mechanical loading (6%), can drive macrophages toward an anti-inflammatory state, thereby may promote inflammation resolution and tissue repair.

Multicentric Retrospective Study on Safety and Efficacy of a Novel Injectable Poly-l-Lactic Acid for Buttocks Recontouring

BACKGROUND

Poly-l-lactic acid (PLLA) injectables have gained increasing attention in aesthetic medicine due to their biocompatibility and long-lasting effects. Although their primary application centers around facial rejuvenation, their potential for off-label use in other body areas has been investigated, demonstrating promising outcomes in terms of both efficacy and safety.

AIM

This study aims to assess the safety and efficacy of a novel 630 mg PLLA-based filler (GANA X), in buttocks treatment.

METHODS

Six physicians treated 51 patients for buttock aesthetic treatment across six different medical facilities in Italy. A survey was filled by both physicians and patients regarding treatment safety, efficacy, and change in quality of life.

RESULTS

We reported minor or mild adverse events, self-resolving within the next few days. Both physicians and patients confirmed notable aesthetic improvements following treatment, varying from moderate to significant enhancement. These effects endured throughout follow-up visits spanning up to 24 months. Patient-reported outcomes indicated elevated self-esteem and improved quality of life posttreatment.

CONCLUSIONS

The high level of satisfaction reported by both physicians and patients highlights the efficacy and tolerability of GANA X filler for buttocks treatment, encouraging their use and research for off-label body areas.

A Systematic Review on the Effectiveness and Safety of Combining Biostimulators with Botulinum Toxin, Dermal Fillers, and Energy-Based Devices

INTRODUCTION

Aesthetic medicine has evolved towards minimally invasive procedures, with biostimulators like Poly-L-Lactic Acid (PLLA), Calcium Hydroxylapatite (CaHA), and Polycaprolactone (PCL) gaining attention for their role in collagen induction, improving skin texture, elasticity, and volume. Combining these agents with other treatments-such as botulinum toxin, dermal fillers, and energy-based devices (e.g. laser and radiofrequency therapies)-is hypothesised to provide enhanced aesthetic outcomes. However, studies on the efficacy and safety of these combinations remain sparse and methodologically varied, posing challenges in establishing definitive recommendations.

METHODS

This systematic review adhered to PRISMA guidelines, involving a thorough literature search across PubMed, MEDLINE, Embase, and Cochrane databases. The search included terms related to biostimulators and combination treatments. Studies meeting inclusion criteria reported clinical outcomes of combined biostimulator treatments, including effectiveness, safety, patient satisfaction, and adverse effects. Key parameters extracted included treatment area, combination protocols, and outcomes. Data synthesis used a narrative approach due to variability in methodologies, treatment protocols, and outcome metrics.

RESULTS

Out of 1,237 studies initially identified, 29 met the inclusion criteria. These studies included various combinations of biostimulators with botulinum toxin, dermal fillers, and energy-based devices, with sample sizes ranging from 10 to 350 subjects. Treatments combining CaHA or PLLA with energy-based modalities like high-intensity focused ultrasound (HIFU), fractional lasers, and microneedling demonstrated notable improvements in skin texture, elasticity, and contouring, particularly in areas with ageing signs. Adverse events included erythema, bruising, and nodules in 15-30% of cases, with rare but severe complications such as granulomas and vascular occlusions. Management protocols for these events involved corticosteroids, hyaluronidase, or surgical intervention. The review also found a lack of molecular understanding of the synergistic mechanisms.

CONCLUSION

The review underscores the potential benefits of combined treatments in aesthetic outcomes, though limitations like heterogeneous methodologies, small sample sizes, and inconsistent protocols impact the reliability of findings. Current literature lacks a molecular understanding of the mechanisms underlying these combinations, limiting insights into the longevity and safety of results. Future studies with standardised protocols, objective outcome measures, and detailed molecular analyses are essential for developing evidence-based recommendations for combining biostimulators with other treatments in aesthetic practice.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors   www.springer.com/00266 .

Single-Cell Sequencing Combined with Transcriptome Sequencing to Explore the Molecular Mechanisms Related to Skin Photoaging

Background

The aging of skin is a diversified biological phenomenon, influenced by a combination of genetic and environmental factors. However, the specific mechanism of skin photoaging is not yet completely elucidated.

Methods

Gene expression profiles for photoaging patients were obtained from the Gene Expression Omnibus (GEO) collection. We conducted single-cell and intercellular communication investigations to identify potential gene sets. Predictive models were created using LASSO regression. The relationships between genes and immune cells were investigated using single sample gene set enrichment analysis (ssGSEA) and gene set variance analysis (GSVA). The molecular processes of important genes were studied using gene enrichment analysis. A miRNA network was created to look for target miRNAs connected with important genes, and transcriptional regulation analysis was used to identify related transcription factors. Finally, merging gene co-expression networks with drug prediction shows molecular pathways of photoaging and potential treatment targets. Furthermore, we validated the role of key genes, immune cell infiltration, and the Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) pathway in photoaging, which were identified through bioinformatics analysis, using in vivo reverse transcription quantitative PCR (RT-qPCR), immunofluorescence labeling, and Western blotting.

Results

This study discovered three key genes, including Atp2b1, Plekho2, and Tspan13, which perform crucial functions in the photoaging process. Immune cell infiltration analysis showed increased M1 macrophages and CD4 memory T cells in the photoaging group. Further signaling pathway analysis indicated that these key genes are enriched in multiple immune and metabolic pathways. The significant roles of Atp2b1, Plekho2, Tspan13, M1 macrophages infiltration, CD4 memory T cells infiltration and the AMPK pathway in photoaging was validated in vivo.

Conclusion

This research revealed the underlying molecular mechanisms of photoaging, indicating that key genes such as Atp2b1 and Tspan13 play crucial roles in the regulation of immune cell infiltration and metabolic pathways. These findings provide a new theory for the treatment of photoaging and provide prospective targets for the advancement of relevant drugs.

Polylactic Acid-Based Polymers Used for Facial Rejuvenation: A Narrative Review

For decades, a diverse range of natural and synthetic materials have been utilized to enhance human tissue and achieve improved aesthetic results. Among these, dermal fillers are some of the most popular treatments. Initially, the primary role of dermal fillers was to restore lost volume. However, with advancements in biomaterial research, a variety of biostimulatory fillers have become essential in aesthetic medicine. One such filler, polylactic acid (PLA), has been extensively used for facial rejuvenation. Upon injection, PLA not only provides immediate volume restoration but also enhances skin quality and appearance while promoting the regeneration of collagen, elastin, and vasculature. This narrative review highlights PLA as a regenerative aesthetic treatment, detailing its physicochemical properties, mechanisms of regeneration stimulation, and clinical applications in facial aesthetics. It represents the cutting-edge foundation upon which further developments can be built to ensure optimal and safe outcomes in treatments using PLA-based collagen stimulators and other similar products for facial rejuvenation. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Poly-L-Lactic Acid Reduces the Volume of Dermal Adipose Tissue Through its Metabolite Lactate

Poly-L-lactic acid (PLLA), a well-established biostimulator that induces collagenases, is widely used among clinical practice to treat skin aging. However, the precise regulatory effect of PLLA on different dermal cell subsets beyond fibroblast has not been fully elucidated. In this study, we constructed in vivo PLLA injection and in vitro PLLA-adipocyte co-culture models to analyze the regulatory effects of PLLA on the volume, differentiation, lipolysis, and thermogenic capacity of dermal adipocyte. We found that PLLA injection significantly reduced the thickness of dermal fat in mice. In co-culture assay, PLLA showed no effect on adipogenesis, but stimulated the lipolysis activity. Interestingly, PLLA also enhanced the differentiation of fat cells into beige fat cells, which possess higher thermogenic capacity. In mechanical study, we blocked adipocyte lactate uptake with a monocarboxylate transporter (MCT1/4) inhibitor and found that the regulatory effect of PLLA on dermal adipocyte relies on its metabolite lactate. In summary, our results suggest that PLLA has complex regulatory effects on the dermal cells, and its ability to improve skin aging is not fully attributed to stimulating collagen synthesis, but also partially involves adipocytes.No Level Assigned This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Investigating the Relationship Between the Emulsification Parameters and Physical-Chemical Properties of Poly(D,L-lactic acid) Particles for Dermal Fillers

Poly(L-lactic acid) (PLLA) and poly(D,L-lactic acid) (PDLLA) particles have been applied as dermal fillers for soft-tissue augmentation because they can induce foreign-body reactions, resulting in fibroblast proliferation and collagen formation. Although PLLA and PDLLA fillers are safe and biocompatible, clinical complications such as nodules and granulomas have been reported, possibly due to incomplete reconstitution. PDLLA particles were prepared via emulsification in this study, and three stirring speeds were investigated when adding PDLLA into carboxymethyl cellulose solution. The particle size, molecular weight of PDLLA, optical rotation, pH value, osmotic pressure, and reconstitution time were analyzed. A rabbit dorsal ear model was established to evaluate the soft-tissue augmentation of a commercial PDLLA filler. The results demonstrated that the stirring speed affected the particle size, but not other physical-chemical properties of the PDLLA particles. All the PDLLA particles were reconstituted in less than 7 min, which is faster than the process for the other commercial PDLLA dermal filler products. In addition, the PDLLA particles could induce inflammation and fibroblast proliferation. Although the PDLLA particles generated in this study have not yet been investigated in vivo, the results demonstrated here suggest their potential for application as dermal fillers.

Poly-D,L-Lactic Acid Fillers Increase Subcutaneous Adipose Tissue Volume by Promoting Adipogenesis in Aged Animal Skin

During aging, subcutaneous white adipose tissue (sWAT) thickness and the adipogenic potential of adipose-derived stem cells (ASCs) decline. Poly-D,L-lactic acid (PDLLA) fillers are commonly used to restore diminished facial volume. Piezo1 increases polarizing macrophages towards the M2 phenotype, which promotes the secretion of fibroblast growth factor 2 (FGF2), thereby increasing ASC survival. This study evaluated whether PDLLA enhances adipogenesis in ASCs by modulating M2 polarization in an in vitro senescence model and in aged animals. Lipopolysaccharide (LPS)-induced senescent macrophages showed decreased Piezo1, which was upregulated by PDLLA. CD163 (an M2 marker) and FGF2 were downregulated in senescent macrophages but were upregulated by PDLLA. We evaluated whether reduced FGF2 secretion from senescent macrophages affects ASCs by applying conditioned media (CM) from macrophage cultures to ASCs. CM from senescent macrophages decreased ERK1/2 and proliferation in ASCs, both of which were restored by CM from PDLLA-stimulated senescent macrophages. Adipogenesis inducers (PPAR-γ and C/EBP-α) were downregulated by CM from senescent macrophages but upregulated by CM from PDLLA-stimulated senescent macrophages in ASCs. Similar patterns were observed in aged animal adipose tissue. PDLLA increased Piezo1 activity, M2 polarization, and FGF2 levels. PDLLA also enhanced ERK1/2, cell proliferation, PPAR-γ, and C/EBP-α expression, leading to increased adipose tissue thickness. In conclusion, our study showed that PDLLA increased adipose tissue thickness by modulating adipogenesis.

Injectable "Skin Boosters" in Aging Skin Rejuvenation: A Current Overview

Aging-related changes in the skin, such as dullness, dehydration, and loss of elasticity, significantly affect its appearance and integrity. Injectable "skin boosters," comprising various biological materials, have become increasingly prominent in addressing these issues, offering rejuvenation and revitalization. This review offers a comprehensive examination of these injectables, detailing their types, mechanisms of action, and clinical uses. It also evaluates the evidence for their effectiveness and safety in treating age-related skin alterations and other conditions. The goal is to provide an insightful understanding of injectable skin boosters in contemporary dermatological practice, summarizing the current state of knowledge.

Comparative Bulk RNA-Seq Analysis of Poly-l-Lactic Acid Versus Calcium Hydroxylapatite Reveals a Novel, Adipocyte-Mediated Regenerative Mechanism of Action Unique to PLLA

BACKGROUND

Injectable biostimulators are widely used to improve facial aging signs. This study was performed to compare the genetic pathways affected by 2 different injectable biostimulators.

METHODS

Randomized 13-week study (n = 21) comparing gene expression after poly l-lactic acid (PLLA-SCA) and calcium hydroxylapatite (CaHA-R) injections (baseline [BL] and Day 28) as treatment of nasolabial fold wrinkles. Punch biopsy was performed at BL and day 90; RNA was isolated, gene expression was analyzed, and bulk RNA sequencing performed. Data from both pathways were studied using the Search Tool for Retrieval of Interacting Genes/Proteins and Reactome databases.

RESULTS

Analysis at Day 0 and Day 90 showed differing gene regulation for PLLA-SCA and CaHA-R (after accounting for minor differences at BL, p < .05 at Day 90 for 9-12 genes). PLLA-SCA uniquely correlates with genes involved in adipocyte regeneration, while CaHA-R did not affect these genes. Clinically, this could translate to healthy fat replacement with an enhanced effect beyond the improvement of the collagen structure and a longer-lasting effect with PLLA-SCA. Furthermore, the adipokines that appear to be upregulated are regenerative with a positive impact on skin health.

CONCLUSION

PLLA-SCA has a novel and unique signature, which supports a potential regenerative mechanism of action through its role in the modulation of adipocyte function.

Lactate triggers KAT8-mediated LTBP1 lactylation at lysine 752 to promote skin rejuvenation by inducing collagen synthesis in fibroblasts

Decreased collagen synthesis by fibroblasts is a key aspect of skin aging. Poly-L-Lactic Acid (PLLA) is a bioabsorbable material that can release lactate continuously, stimulating endogenous collagen synthesis in the skin. Herein, this study aimed to investigate the impact of PLLA-released lactate on collagen production in fibroblasts for skin rejuvenation. Human fibroblasts were exposed to varying concentrations of PLLA in vitro, while PLLA was injected into the back skin of aged mice in vivo. Safety and efficacy of PLLA on collagen synthesis and skin rejuvenation were evaluated through Calcein-AM/PI staining, EdU proliferation assay, and analysis of collagen I and collagen III expression in fibroblasts using western blotting and immunofluorescence. To elucidate the underlying mechanisms, lactate contents in cell-free supernatant and cell lysates from PLLA-treated fibroblasts, as well as total lysine lactylation (Pan Kla) levels were measured. Additionally, we found that fibroblasts can uptake extracellular lactate released from PLLA through monocarboxylate transporter-1 (MCT1) to facilitate latent-transforming growth factor beta-binding protein 1 (LTBP1) lactylation at lysine 752 (K752) via a KAT8-dependent mechanism, then increases the protein levels of collagen I and collagen III in fibroblasts. Overall, this study highlights a valuable insight into lactylation modification of non-histone protein for skin rejuvenation.

Agarose-collagen composite microsphere implants: A biocompatible and robust approach for skin tissue regeneration

Photoaged skin, a consequence of UV radiation-induced collagen degradation, presents a significant challenge for skin rejuvenation. Synthetic polymer microspheres, while offering collagen regeneration potential, carry risks like granulomas. To overcome this, we developed a novel agarose-collagen composite microsphere implant for skin tissue regeneration. Fabricated using an emulsification-crosslinking method, these microspheres exhibited excellent uniformity and sphericity (with a diameter of ~38.5 μm), as well as attractive injectability. In vitro studies demonstrated their superior biocompatibility, promoting cell proliferation, adhesion, and migration. Further assessments revealed favorable biosafety and blood compatibility. In vivo experiments in photoaged mice showed that implantation of these microspheres effectively reduced wrinkles, increased skin density, and improved elasticity by stimulating fibroblast encapsulation and collagen regeneration. These findings highlight the potential of agarose-collagen microspheres in dermatological and tissue engineering applications, offering a safer alternative for skin rejuvenation.

Efficacy and Safety of Poly-l-Lactic Acid in Facial Aesthetics: A Systematic Review

The primary objective of this systematic review study was to investigate the effectiveness, durability, and adverse events of PLLA treatment for aesthetic indications. The search strategy was performed in MEDLINE (Ovid). The electronic literature search of five databases was performed, from the inception of the databases until the 12th of February 2024. This was to identify randomized clinical trials that assessed PLLA treatment in adult individuals exhibiting facial aging and/or facial lipoatrophy. Risk of bias was assessed using the Cochrane Risk-of-Bias Tool for Randomized Trials (RoB 2). Eleven RCTs out of 1467 identified citations were included. Four studies showed increased dermal thickness, significant improvement in facial lipoatrophy severity and aesthetic clinical scores, after PLLA treatment with its effects sustained for at least 25 months. Two studies demonstrated the superiority of PLLA over injectable human collagen. Also, three studies showed positive results favoring PLLA when compared with PH gel in lipoatrophy severity, transepidermal water loss, skin quality, elasticity, and patient satisfaction. All adverse events were mild-to-moderate in intensity, and the main ones worth noting were bruising, hematoma, tenderness, nodules, and edema. Five out of eleven studies were considered having high risk of bias. The evidence on the effectiveness and safety of PLLA for facial rejuvenation is of low quality; thus, the reported high effectiveness, safety, and long-lasting effects for this purpose should be further investigated.

Deep skin fibroblast-mediated macrophage recruitment supports acute wound healing

Epithelial and immune cells have long been appreciated for their contribution to the early immune response after injury; however, much less is known about the role of mesenchymal cells. Using single nuclei RNA-sequencing, we defined changes in gene expression associated with inflammation at 1-day post-wounding (dpw) in mouse skin. Compared to keratinocytes and myeloid cells, we detected enriched expression of pro-inflammatory genes in fibroblasts associated with deeper layers of the skin. In particular, SCA1+ fibroblasts were enriched for numerous chemokines, including CCL2, CCL7, and IL33 compared to SCA1- fibroblasts. Genetic deletion of Ccl2 in fibroblasts resulted in fewer wound bed macrophages and monocytes during injury-induced inflammation with reduced revascularization and re-epithelialization during the proliferation phase of healing. These findings highlight the important contribution of deep skin fibroblast-derived factors to injury-induced inflammation and the impact of immune cell dysregulation on subsequent tissue repair.

Macrophage plasticity: signaling pathways, tissue repair, and regeneration

Macrophages are versatile immune cells with remarkable plasticity, enabling them to adapt to diverse tissue microenvironments and perform various functions. Traditionally categorized into classically activated (M1) and alternatively activated (M2) phenotypes, recent advances have revealed a spectrum of macrophage activation states that extend beyond this dichotomy. The complex interplay of signaling pathways, transcriptional regulators, and epigenetic modifications orchestrates macrophage polarization, allowing them to respond to various stimuli dynamically. Here, we provide a comprehensive overview of the signaling cascades governing macrophage plasticity, focusing on the roles of Toll-like receptors, signal transducer and activator of transcription proteins, nuclear receptors, and microRNAs. We also discuss the emerging concepts of macrophage metabolic reprogramming and trained immunity, contributing to their functional adaptability. Macrophage plasticity plays a pivotal role in tissue repair and regeneration, with macrophages coordinating inflammation, angiogenesis, and matrix remodeling to restore tissue homeostasis. By harnessing the potential of macrophage plasticity, novel therapeutic strategies targeting macrophage polarization could be developed for various diseases, including chronic wounds, fibrotic disorders, and inflammatory conditions. Ultimately, a deeper understanding of the molecular mechanisms underpinning macrophage plasticity will pave the way for innovative regenerative medicine and tissue engineering approaches.

Piezo1 Activation Drives Enhanced Collagen Synthesis in Aged Animal Skin Induced by Poly L-Lactic Acid Fillers

Poly L-lactic acid (PLLA) fillers stimulate collagen synthesis by activating various immune cells and fibroblasts. Piezo1, an ion channel, responds to mechanical stimuli, including changes in extracellular matrix stiffness, by mediating Ca2+ influx. Given that elevated intracellular Ca2+ levels trigger signaling pathways associated with fibroblast proliferation, Piezo1 is a pivotal regulator of collagen synthesis and tissue fibrosis. The aim of the present study was to investigate the impact of PLLA on dermal collagen synthesis by activating Piezo1 in both an H2O2-induced cellular senescence model in vitro and aged animal skin in vivo. PLLA elevated intracellular Ca2+ levels in senescent fibroblasts, which was attenuated by the Piezo1 inhibitor GsMTx4. Furthermore, PLLA treatment increased the expression of phosphorylated ERK1/2 to total ERK1/2 (pERK1/2/ERK1/2) and phosphorylated AKT to total AKT (pAKT/AKT), indicating enhanced pathway activation. This was accompanied by upregulation of cell cycle-regulating proteins (CDK4 and cyclin D1), promoting the proliferation of senescent fibroblasts. Additionally, PLLA promoted the expression of phosphorylated mTOR/S6K1/4EBP1, TGF-β, and Collagen I/III in senescent fibroblasts, with GsMTx4 treatment mitigating these effects. In aged skin, PLLA treatment similarly upregulated the expression of pERK1/2/ERK1/2, pAKT/AKT, CDK4, cyclin D1, mTOR/S6K1/4EBP1, TGF-β, and Collagen I/III. In summary, our findings suggest Piezo1's involvement in PLLA-induced collagen synthesis, mediated by heightened activation of cell proliferation signaling pathways such as pERK1/2/ERK1/2, pAKT/AKT, and phosphorylated mTOR/S6K1/4EBP1, underscoring the therapeutic potential of PLLA in tissue regeneration.

A morphological analysis of calcium hydroxylapatite and poly-l-lactic acid biostimulator particles

Injectable fillers, pivotal in aesthetic medicine, have evolved significantly with recent trends favoring biostimulators like calcium hydroxylapatite (CaHA-CMC; Radiesse, Merz Aesthetics, Raleigh, NC) and poly-l-lactic acid (PLLA; Sculptra Aesthetics, Galderma, Dallas, TX). This study aims to compare the particle morphology of these two injectables and examine its potential clinical implications. Utilizing advanced light and scanning electron microscopy techniques, the physical characteristics of CaHA-CMC and PLLA particles were analyzed, including shape, size, circularity, roundness, aspect ratio, and quantity of phagocytosable particles. The findings reveal several morphological contrasts: CaHA-CMC particles exhibited a smooth, homogenous, spherical morphology with diameters predominantly ranging between 20 and 45 µm, while PLLA particles varied considerably in shape and size, appearing as micro flakes ranging from 2 to 150 µm in major axis length. The circularity and roundness of CaHA-CMC particles were significantly higher compared to PLLA, indicating a more uniform shape. Aspect ratio analysis further underscored these differences, with CaHA-CMC particles showing a closer resemblance to circles, unlike the more oblong PLLA particles. Quantification of the phagocytosable content of both injectables revealed a higher percentage of phagocytosable particles in PLLA. These morphological distinctions may influence the tissue response to each treatment. CaHA-CMC's uniform, spherical particles may result in reduced inflammatory cell recruitment, whereas PLLA's heterogeneous particle morphology may evoke a more pronounced inflammatory response.

Poly-l-lactic acid microspheres delay aging of epidermal stem cells in rat skin

Objective

Injectable skin fillers offer a wider range of options for cutaneous anti-aging and facial rejuvenation. PLLA microspheres are increasingly favored as degradable and long-lasting fillers. The present study focused solely on the effect of PLLA on dermal collagen, without investigating its impact on the epidermis. In this study, we investigated the effects of PLLA microspheres on epidermal stem cells (EpiSCs).

Methods

Different concentrations of PLLA microspheres on epidermal stem cells (EpiSCs) in vitro through culture, and identification of primary rat EpiSCs. CCK-8 detection, apoptosis staining, flow cytometry, Transwell assay, wound healing assay, q-PCR analysis, and immunofluorescence staining were used to detect the effects of PLLA on EpiSCs. Furthermore, we observed the effect on the epidermis by injecting PLLA into the dermis of the rat skin in vivo.

Results

PLLA microspheres promote cell proliferation and migration while delaying cell senescence and maintaining its stemness. In vitro, Intradermal injection of PLLA microspheres in the rat back skin resulted in delayed aging, as evidenced by histological and immunohistochemical staining of the skin at 2, 4, and 12 weeks of follow-up.

Conclusion

This study showed the positive effects of PLLA on rat epidermis and EpiSCs, while providing novel insights into the anti-aging mechanism of PLLA.

An evaluation of the effectiveness of 'ULTRACOL 200' in enhancing nasolabial fold wrinkles through cutaneous repair

BACKGROUND

Injectable filler, a nonsurgical beauty method, has gained popularity in rejuvenating sagging skin. In this study, polydioxanone (PDO) was utilized as the main component of the ULTRACOL200 filler that helps stimulate collagenesis and provide skin radiant effects. The study aimed to evaluate and compare the effectiveness of ULTRACOL200 with other commercialized products in visually improving dermatological problems.

METHODS

Herein, 31 participants aged between 20 and 59 years were enrolled in the study. 1 mL of the testing product, as well as the quantity for the compared groups was injected into each participants face side individually. Subsequently, skin texture and sunken volume of skin were measured using ANTERA 3D CS imaging technology at three periods: before the application, 4 weeks after the initial application, and 4 weeks after the 2nd application of ULTRACOL200.

RESULTS

The final results of skin texture and wrinkle volume evaluation consistently demonstrated significant enhancement. Consequently, subjective questionnaires were provided to the participants to evaluate the efficacy of the testing product, illustrating satisfactory responses after the twice applications.

CONCLUSION

The investigation has contributed substantially to the comprehension of a PDO-based filler (ULTRACOL200) for skin enhancement and provided profound insight for future clinical trials.

Skin rejuvenation effect of the combined PDLLA and non cross-linked hyaluronic acid: A preliminary study

BACKGROUND

Skin aging is characterized by wrinkles, rough skin texture, pigmentation, facial erythema, and telangiectasia through structural and functional changes in the epidermis and dermis. Recently, injectable poly(D, L-lactic acid), a biodegradable polymer, has been used widely for skin rejuvenation.

AIMS

This study aims to assess the efficacy and safety of injectable dermal poly D, L-lactic acid) for skin rejuvenation.

PATIENTS/METHODS

A total of 16 patients who desired skin rejuvenation were included. All participants received two or three procedure sessions with a 4 weeks interval between sessions. Clinical and three-dimensional images at baseline, before each procedural session, and follow-up visits were obtained. Therapeutic effects were assessed by evaluating signs of aging skin and overall improvement by dermatologists and patients. Histologic examinations with special stains were performed on the posterior auricular areas of consenting patients at baseline and follow-up visits after injecting poly D L-lactic acid into the postauricular area as in the face.

RESULTS

Overall, statistically significant differences were observed in all signs of aging skin, such as fine wrinkles, skin texture, irregular pigmentation, telangiectasia, and facial erythema before and after treatments. Half (50%) of patients responded that there was more than 50% overall improvement. There were no severe adverse events. Histologic examination demonstrated increases in collagen and elastic fibers in the dermis.

CONCLUSIONS

Results of this preliminary study suggest that injectable dermal poly D, L-lactic acid can significantly affect skin rejuvenation without causing any serious adverse events.

Needle-Free Jet Injection of Poly-(Lactic Acid) for Atrophic Acne Scars: Literature Review and Report of Clinical Cases

Acne scars, particularly atrophic ones, present a persistent challenge in cosmetic medicine and surgery, requiring extended and multifaceted treatment approaches. Poly-(lactic acid) injectable fillers show promise in managing atrophic acne scars by stimulating collagen synthesis. However, the utilization of needle-free injectors for delivering poly-(lactic acid) into scars remains an area requiring further exploration. In this article, a summary of the latest advancements in needle-free jet injectors is provided, specifically highlighting the variations in jet-producing mechanisms. This summary emphasizes the differences in how these mechanisms operate, offering insights into the evolving technology behind needle-free injection systems. The literature review revealed documented cases focusing on treating atrophic acne scars using intralesional poly-(lactic acid) injections. The results of these clinical studies could be supported by separate in vitro and animal studies, elucidating the feasible pathways through which this treatment operates. However, there is limited information on the use of needle-free jet injectors for the intradermal delivery of poly-(lactic acid). Clinical cases of atrophic acne scar treatment are presented to explore this novel treatment concept, the needle-free delivery of poly-(lactic acid) using a jet pressure-based injector. The treatment demonstrated efficacy with minimal adverse effects, suggesting its potential for scar treatment. The clinical efficacy was supported by histological evidence obtained from cadaver skin, demonstrating an even distribution of injected particles in all layers of the dermis. In conclusion, we suggest that novel needle-free injectors offer advantages in precision and reduce patient discomfort, contributing to scar improvement and skin rejuvenation. Further comprehensive studies are warranted to substantiate these findings and ascertain the efficacy of this approach in scar treatment on a larger scale.

Alloplastic Epidermal Skin Substitute in the Treatment of Burns

The goal of burn wound treatment is to ensure rapid epithelialization in superficial burns and the process of rebuilding the lost skin in deep burns. Topical treatment plays an important role. One of the innovations in the field of synthetic materials dedicated to the treatment of burns is epidermal skin substitutes. Since the introduction of Suprathel®, the alloplastic epidermal substitute, many research results have been published in which the authors investigated the properties and use of this substitute in the treatment of wounds of various origins, including burn wounds. Burn wounds cause both physical and psychological discomfort, which is why ensuring comfort during treatment is extremely important. Alloplastic epidermal substitute, due to its biodegradability, plasticity, no need to remove the dressing until healing, and the associated reduction in pain, is an alternative for treating burns, especially in children.

PLA-HPG based coating enhanced anti-biofilm and wound healing of Shikonin in MRSA-infected burn wound

Burn wounds are susceptible to bacterial infections, including Methicillin-resistant Staphylococcus aureus (MRSA), which typically form biofilms and exhibit drug resistance. They also have specific feature of abundant exudate, necessitating frequent drug administration. Shikonin (SKN) has been reported to reverse MRSA drug resistance and possesses anti-biofilm and wound healing properties, however, it suffers from drawbacks of low solubility and instability. In this study, we developed PLA-HPG based bioadhesive nanoparticles SKN/BNP, which demonstrated a drug loading capacity of about 3.6%, and exhibited sustained-release behavior of SKN. The aldehyde groups present on the surface of BNP improved the local adhesion of SKN/BNP both in vitro and in vivo, thereby reducing the frequency of drug dosing in exudate-rich burn wounds. BNP alone enhanced proliferation and migration of the fibroblast, while SKN/BNP promoted fibroblast proliferation and migration as well as angiogenesis. Due to its bioadhesive property, BNP directly interacted with biofilm and enhanced the efficacy of SKN against MRSA biofilm in vitro. In a mouse model of MRSA-infected burn wounds, SKN/BNP demonstrated improved anti-biofilm and wound healing efficiency. Overall, our findings suggest that SKN/BNP holds great promise as a novel and effective treatment option for clinical applications in MRSA-infected burn wounds.